Computer graphics processing and selective visual display system – Plural physical display element control system – Display elements arranged in matrix
Reexamination Certificate
2000-07-21
2003-10-14
Shalwala, Bipin (Department: 2673)
Computer graphics processing and selective visual display system
Plural physical display element control system
Display elements arranged in matrix
C345S001300, C345S051000, C345S090000, C345S098000, C345S214000
Reexamination Certificate
active
06633274
ABSTRACT:
BACKGROUND OF THE INVENTION
The present invention relates to technology for controlling display and, specifically, to technology that can be particularly effectively adapted to controlling the drive of liquid crystal, such as technology that can be effectively utilized in a display control circuit in a dot-matrix liquid crystal panel for displaying characters or in a liquid crystal panel having a function of displaying pictures, marks, icons, characters (figures), etc. independently of the dot-matrix character display.
A liquid crystal display device, in general, comprises a liquid crystal display panel, a liquid crystal display controller formed as an integrated circuit on a semiconductor substrate for driving the liquid crystal display panel, and a microprocessor (MPU) or a microcontroller including a microprocessing unit (CPU) for controlling the writing of display data or the display operation of the liquid crystal display controller.
A liquid crystal display controller including a character generator for forming a display pattern of dot-matrix type is constituted by a display data memory for storing character codes (hereinafter referred to as a random access memory for display data or a display data RAM), a character generator memory for storing character patterns such as character fonts (hereinafter referred to as a read-only memory for a character generator or a character generator ROM), an address counter for reading display data from the display data RAM in accordance with the drive position of the liquid crystal display panel, a liquid crystal drive circuit for driving the liquid crystal by generating drive signals for common electrodes and for segment electrodes of a liquid crystal display panel, and a timing generation circuit for generating clock signals that give display timings.
The microprocessor writes, onto the display data RAM, character codes corresponding to characters to be displayed on the liquid crystal display panel. An address counter successively reads out character codes from the display data RAM in accordance with the drive position of the liquid crystal display panel, and successively reads out character patterns by making access to the character generator ROM by using character codes that are read out as part of the addresses. The character patterns that are read out are successively sent, as liquid crystal turn-on/off data, to a segment shift register in the liquid crystal drive circuit. When the data of one line are accumulated, the whole segment driver circuits output the drive voltages of the turn-on/turn-off level simultaneously thereby to drive the liquid crystal display panel.
Each character is constituted by a plurality of lines in a vertical direction and, hence, the above-mentioned control operation is repeated by the number of lines of the character for every display row (8 lines when the character comprises 5 (horizontal)×8 (vertical) dots). The turn-on/turn-off control operation for the display is executed in a time-division manner for each of the lines. Therefore, a selection signal of one line generated from the timing control circuit is sent to a common shift register. As the shift register shifts for each line, a common driver successively outputs a drive voltage of the selection level of the line.
SUMMARY OF THE INVENTION
In a portable telephone set or a portable electronic device such as a pager mounted with the above-mentioned liquid crystal display device, there is no need to produce a display on the whole surface of the liquid crystal display panel during the wait time; i.e., only a minimum of display may be made, such as the display of a calendar, the display of time, a mark called a pictogram or icons. In the liquid crystal display device in a portable telephone set or the like, however, the amount of display is decreased during the wait time but the liquid crystal drive duty is not changed. That is, even the common electrodes of lines that are not displayed are scanned, too, involving a problem that the consumption of electric power cannot be reduced to a sufficient degree during the wait time.
In a liquid crystal display controller having 32 common drivers for, for example, 32 lines are successively and selectively driven, by successively selecting from a common driver corresponding to a signal COM
1
to a common driver corresponding to a signal COM
32
. A method of successively driving such common signal lines of 32 lines is called 1/32 duty drive. In this case, if the character font has a size of 5×8 dots, character strings of 4 rows can be displayed on the liquid crystal panel in the vertical direction. When this liquid crystal display controller is driven for 4 rows in a time-division manner even though 4 rows need not be displayed on the whole surface, the voltage for driving the liquid crystal and the current consumed by the liquid crystal display controller become the same as those of when 4 rows are displayed on the whole surface.
Here, if 4 rows are not displayed on the whole surface during the stand-by state of the system, but if part of the rows is selectively driven, the duty for driving the liquid crystal is lowered, the voltage for driving the liquid crystal is lowered, and then, less electric power is consumed by the liquid crystal drive controller. However, a change in the voltage for driving the liquid crystal results in a change in the optimum drive bias ratio, making it impossible to obtain a favorable display contrast under the unchanged drive condition. Besides, if only the duty for driving the liquid crystal is simply lowered, then, the display position of the character font is fixed to the uppermost row, causing a problem of poor balance of view from the standpoint of display.
Japanese Utility Model Laid-Open No. 131786/1990 discloses a liquid crystal matrix display device having a 4-power boosting circuit and a 6-power boosting circuit, and for selecting either of the boosting circuits depending upon the duty for driving the liquid crystal. Japanese Patent Laid-Open No. 119385/1991 discloses a liquid crystal display circuit capable of being switchably driven by a plurality of power supplies such as an AC power supply, battery, etc., by which the device is driven in case of power failure, and a minimum of information such as a time piece and the like are displayed at a decreased drive duty with a lowered bias.
It is an object of the present invention to provide a liquid crystal display controller mounted in an electronic device, wherein the duty for driving the liquid crystal is dynamically changed depending upon the operation state of the system in order to decrease a total amount of electric power consumed by the system, and, when a variable duty display is made, an optimum liquid crystal drive voltage and an optimum liquid crystal drive bias condition are easily set depending upon the duty for driving liquid crystal.
Another object of the present invention is to provide a liquid crystal display controller capable of dynamically varying the boosting power of the boosted voltage, the duty for driving the liquid crystal, the bias for driving the liquid crystal and the liquid crystal display position, and a system using the above liquid crystal display controller.
A further object of the present invention is to provide a liquid crystal display controller capable of producing a display that is most easily viewed depending upon the operation state of the system and a system using the above liquid crystal display controller.
Representative aspects of the invention disclosed in this application will be briefly described below.
In the liquid crystal display controller are provided a drive duty selection register (also referred to as display line control register) that can be rewritten from a microprocessor and a drive bias selection register. In a liquid crystal display panel capable of displaying 4 rows, when the whole surface display (e.g., 4-row display) is changed to the display of a few rows only (e.g., 1-row display), preset values of the drive duty selection register and of the drive
Higuchi Kazuhisa
Sakamaki Gorou
Sugiyama Kimihiko
Tani Kunihiko
Yamamoto Katsuhiko
Kovalick Vincent E.
Mattingly Stanger & Malur, P.C.
Shalwala Bipin
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